The invention relates generally to the field of printing and, more particularly, to a method of making a print head that utilizes a functionally gradient piezoelectric element.
Piezoelectric ink jet elements are used in a wide range of microfluidic printing devices. Conventional ink jet elements utilize piezoelectric transducers that comprise one or more uniformly polarized piezoelectric elements with attached surface electrodes. The three most common transducer configurations are multilayer ceramic, monomorph or bimorphs, and flextensional composite transducers. To activate a transducer, a voltage is applied across its electrodes thereby creating an electric field throughout the piezoelectric elements. This field induces a change in the geometry of the piezoelectric elements resulting in elongation, contraction, shear or combinations thereof. The induced geometric distortion of the elements can be used to implement motion or perform work. In particular, piezoelectric bimorph transducers that produce a bending motion, are commonly used in micropumping devices. However, a drawback of the conventional piezoelectric bimorph transducer is that two bonded piezoelectric elements are needed to implement the bending. These bimorph transducers are typically difficult and costly to manufacture for micropumping applications (in this application, the word micro means that the dimensions of the element range from 100 microns to 10 mm). Also, when multiple bonded elements are used, stress induced in the elements due to their constrained motion can damage or fracture an element due to abrupt changes in material properties and strain at material interfaces.
Therefore, a need persists for an ink jet head that overcomes the aforementioned problems associated with conventional ink jet apparatus.
It is, therefore, an object of the present invention to provide a method of making a print head that utilizes a novel piezoelectric element.
It is another object of the invention to provide a method that utilizes a slab of piezoelectric material having a functionally gradient d-coefficient selected so that the material changes its geometry in response to an electric field in the slab.
Yet another object of the invention is to provide a method that enables any one of a plurality of independent fluid containment compartment to be activated for channeling fluid.
It is a feature of the invention that the method of making a print head includes the step of providing a plurality of independent fluid containment compartments each having a piezoelectric transducer having a functionally gradient d-coefficient for activating the flow of fluid therethrough.
To accomplish the several objects and advantages of the invention, there is provided a method of making a print head, comprising the steps of:
(a) forming a body having a closed base and a plurality of open independent fluid containment compartments formed about the base, each compartment having at least one inlet orifice and at least one outlet orifice;
(b) providing a substantially planar piezoelectric transducer comprising a slab of piezoelectric material having a first surface and an opposing second surface for enclosing said open independent fluid containment compartments, said piezoelectric material being provided having a functionally gradient d-coefficient selected so that said slab changes geometry in response to an applied voltage which produces an electric field in the slab;
(c) providing a plurality of first electrodes and a second electrode;
(d) arranging each one of said plurality of first electrodes on said first surface of said slab of piezoelectric material and said second electrodes on said second surface;
(e) arranging said piezoelectric transducer on said open independent fluid containment compartment such that each one of said plurality of first electrodes and a portion of said second electrode are operably associated with each one of said plurality of independent fluid containment compartments;
(f) providing a source of fluid composition in fluid communications with each one of said inlet orifices of each one of said independent fluid containment compartments; said source being arranged for channeling said fluid composition through an inlet orifice of said at least one of said plurality of independent fluid containment compartments; and,
(g) providing a source of power operably associated with each one of said first electrodes and said second electrode such that energizing any one of said plurality of first electrodes and said second electrode associated with any one of said independent fluid containment compartments enables said fluid composition to flow through said outlet orifice of one of said one independent fluid containment compartments.
An important advantage of the method of the present invention is that it provides for the utilization of a piezoelectric actuating element that comprises a single slab of piezoelectric material having a functionally gradient d-coefficient to implement droplet ejection, thereby eliminating the need for multilayered or composite piezoelectric structures. Moreover, a further advantage of the present method is that the slab of piezoelectric material provided for has a longer operational life span because it eliminates the stress induced fracturing that occurs in multilayered or composite piezoelectric transducers.